Management has warned that the payments, which average €1,200-1,400 per employee, will be withheld until the row has been resolved.

The move sparked a furious response from SIPTU, which this week served Aer Lingus with strike notice for the eve of the St Patrick's weekend.

However, union officials have been strongly condemned for "targeting" the St Patrick's weekend and were accused last night of "using people for leverage".

Hundreds of thousands of passengers face the prospect of travel chaos if the four-hour strike, scheduled for March 14, goes ahead.

But tensions between the union and the company escalated last night after it emerged that staff now face the prospect of having their productivity payments frozen.

The payments, totalling €6.25m this year, were agreed under a previous agreement known as 'Greenfield' and were due to be paid out in lump sums over the coming weeks.

The Irish Independent understands that the threat was made by Aer Lingus CEO Christophe Mueller during a meeting with staff members.

A spokeswoman confirmed last night that even non-SIPTU members will be affected by the decision to freeze the payment.

SIPTU has branded the threat as "outrageous" and said it only served to undermine the ongoing negotiations about the Aer Lingus pension fund.

"This is nothing short of scandalous and it will cause deep alarm among staff. This payment is made to all staff, from pilots to those on lower pay and it really does make a difference," SIPTU organiser Dermot O'Loughlin said.

The union has shown no sign of backtracking on its threat to strike on March 14 in a move that will cause chaos.

Aer Lingus is now examining whether to reschedule a number of flights to Paris on the eve of St Patrick's weekend because of the growing threat of strike action.

Flights carrying hundreds of Irish rugby fans to the French capital for the crunch Six Nations decider are scheduled to depart during the middle of the planned work stoppages.

SCHEDULES

Management has begun drawing up contingency plans which includes the option of rescheduling flights scheduled to depart between 5-9am, when workers are due to down their tools. The strike is due to affect Cork, Dublin and Shannon airports.

Flights leaving Ireland for the UK, Europe, the US and the Gulf are also likely to be delayed or cancelled due to backlogs caused by the action.

It has emerged that hundreds of Irish fans scheduled to depart from Dublin for Paris on 7am and 8am flights face the prospect of being grounded.

Thousands of people returning from Cheltenham are also expected to be affected.

Transport Minister Leo Varadkar said he believed SIPTU had "made the wrong call". He said: "They're targeting St Patrick's Day, which will discommode hundreds of thousands of tourists and hundreds of thousands trying to get away for a hard-earned weekend.

"They're (SIPTU) the only ones who can call off this strike. This strike hasn't been called by Government, hasn't been called by Aer Lingus or the airport companies, it's been called by SIPTU, who haven't even balloted their members on the latest set of proposals."

A deal was brokered in the Labour Court last year to help address a near-€800m deficit at a defined benefit pension scheme, the Irish Airlines Superannuation Scheme (IASS).

But plans by the IASS trustee to address the deficit hit a roadblock. Under fresh proposals from the trustee, retired as well as active IASS members are facing cuts of up to 20pc in their pension entitlements and accrued benefits.